The NEC put out by the NFPA is only a suggested guideline, not a law.
I have posted it for your guidance, to be compete. I don't want you to be caught off guard and have you say: "Why didn't you tell me?" The local AHJ (Authority Having Jurisdiction), who is usually the electrical inspector, is free to decide how it should be done. His decision then becomes the local law and is binding on you and the local electricians.
The code is written in esoteric language, best understood by an electrical professional, which I'm not.
The code not only says that the mast and the coax shield should be grounded, but they should be connected with separate wires to the house electrical system ground.
The ground for the mast is to drain away any buildup of static charge to discourage a strike and to shunt any current to ground if a hot wire contacts the mast. The grounding block grounds the coax shield to help reject electrical interference and to shunt any voltage to ground if the shield becomes energized by defective electrical equipment connected to the coax.
The last reason is most important to me because I have had three close calls with electrical shock. The coax is connected to AC operated equipment. All AC operated equipment has leakage current, even when operating properly. If the equipment has a 3-wire power cord that is connected to a properly wired 3-wire outlet, any leakage current will be shunted to ground. If your equipment has a 2-wire power cord and becomes defective, you are at risk from electrical shock.
I bought a leakage current tester to check my equipment and any equipment that I was giving to other people.
Some of the dish installers use a piggy back-method of grounding. The coax between the antenna and the grounding block has an external grounding conductor of 17gauge copper clad steel that grounds the mast (or dish) and is connected to the grounding block. Then, there is only one 10 gauge wire from the grounding block to the house electrical system ground.
http://www.dbsinstall.com/diy/Grounding-2.asp
If the ground connections to the cold water pipe were done by electricians, that indicates to me they would have satisfied the local laws.
You get to decide how you want to do it.